<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,minimum-scale=1,user-scalable=no">
    <title></title>
</head>
<body>
    <h1>Shadow DOM</h1>
    <button>Hello, world!</button>
    <script>
        var host = document.querySelector('button')
        var root = host.createShadowRoot()
        root.textContent = 'Hello, Shadow DOM!';
    </script>
</body>
</html>
